Amine-initiated polyols and rigid polyurethane foam made therefrom

ABSTRACT

Polyether polyols are initiated with aminocyclohexanealkylamines such as isophoronediamine and 1,8-diaminop-menthane. The polyols are useful in making rigid polyurethane foams, especially foams for pour-in-place applications, where they give a good combination of low k-factor and short demold times.

This application claims benefit of U.S. Provisional Application No.60/898,367, filed 30 Jan. 2007.

This invention pertains to polyols that are useful for manufacturingrigid polyurethane foams, as well as rigid foams made from thosepolyols.

Rigid polyurethane foams have been used widely for several decades asinsulation foam in appliances and other applications, as well as avariety of other uses. These foams are prepared in a reaction of apolyisocyanate and one or more polyol, polyamine or aminoalcoholcompounds. The polyol, polyamine or aminoalcohols compounds can becharacterized as having equivalent weights per isocyanate-reactive groupin the range of up to about 300 and an average of more than threehydroxyl and/or amino groups per molecule. The reaction is conducted inthe presence of a blowing agent which generates a gas as the reactionproceeds. The gas expands the reacting mixture and imparts a cellularstructure.

Originally, the blowing agent of choice was a “hard” chlorofluorcarbon(CFC) such as trichlorofluoromethane or dichlorodifluoromethane. TheseCFCs processed very easily and produced foam having very good thermalinsulation properties. However, the CFC blowing agents have been phasedout because of environmental concerns.

CFCs have been replaced with other blowing agents such ashydrofluorocarbons, low-boiling hydrocarbons, hydrochloroflurocarbons,ether compounds, and water (which reacts with isocyanates to generatecarbon dioxide). For the most part, these alternative blowing agents areless effective thermal insulators than their CFC predecessors. Theability of a foam to provide thermal insulation is often expressed interms of “k-factor”, which is a measure of the amount of heat that istransferred through the foam per unit area per unit time, taking intoaccount the thickness of the foam and the applied temperature differenceacross the foam thickness. Foams produced using alternative blowingagents tend to have higher k-factors than those produced using “hard”CFC blowing agents. This has forced rigid foam producers to modify theirfoam formulations in other ways to compensate for the loss of thermalinsulation values that result from the changes in blowing agent. Many ofthese modifications focus on reducing cell size in the foam.Smaller-sized cells tend to provide better thermal insulationproperties.

It has been found that modifications to a rigid foam formulation whichimprove k-factor tend to affect the processing characteristics of theformulation in an undesirable way. The curing characteristics of theformulation are important, especially in pour-in-place applications suchas appliance foam. Refrigerator and freezer cabinets, for example, areusually insulated by partially assembling an exterior shell and interiorliner, and holding them in position such that a cavity is formed betweenthem. This is often done using a jig or other apparatus. The foamformulation is introduced into the cavity, where it expands to fill thecavity. The foam provides thermal insulation and imparts structuralstrength to the assembly. The way the foam formulation cures isimportant in at least two respects. First, the foam formulation mustcure quickly to form a dimensionally stable foam, so that the finishedcabinet can be removed from the jig. This characteristic is generallyreferred to as “demold” time, and directly affects the rate at whichcabinets can be produced.

In addition, the curing characteristics of the system affect a propertyknown as “flow index” or simply “flow”. A foam formulation will expandto a certain density (known as the ‘free rise density’) if permitted toexpand against minimal constraints. When the formulation must fill arefrigerator or freezer cabinet, its expansion is somewhat constrainedin several ways. The foam must expand mainly in a vertical (rather thanhorizontal) direction within a narrow cavity. As a result, theformulation must expand against a significant amount of its own weight.The foam formulation also must flow around corners and into all portionsof the wall cavities. In addition, the cavity often has limited or noventing, and so the atmosphere in the cavity exerts additional pressureon the expanding foam. Because of these constraints, a greater amount ofthe foam formulation is needed to fill the cavity than would bepredicted from the free rise density alone. The amount of foamformulation needed to minimally fill the cavity can be expressed as aminimum fill density (the weight of the formulation divided by thecavity volume). The ratio of the minimum fill density to the free risedensity is the flow index. The flow index is ideally 1.0, but is on theorder of 1.2 to 1.8 in commercially practical formulations. Lower flowindex is preferred, all other things being equal, because raw materialscosts are lower when a smaller weight of foam is needed.

Modifications to foam formulations that favor low k-factor tend to havean adverse effect on demold time, flow index or both. Therefore,although formulations have been developed which closely matchconventional CFC-based formulations in k-factor, the overall cost ofusing these formulations is often higher due to lower productivity(because of greater demold times), higher raw material costs (because ofhigher flow index) or both.

What is desired is a rigid foam formulation that provides a low k-factorfoam with a low flow index and a short demold time.

This invention is in one aspect an amine-initiated polyol having anaverage hydroxyl functionality of greater than 3.0 up to 4.0, the polyolbeing a reaction product of at least one C₂-C₄ alkylene oxide with anaminocyclohexanealkylamine initiator compound.

The invention is also a process for preparing a rigid polyurethane foam,comprising

-   a) forming a reactive mixture containing at least-   1) an aminocyclohexanealkylamine-initiated polyol according to the    first aspect of the invention having a hydroxyl equivalent weight of    from 75 to 560, or mixture thereof with at least one other polyol,    provided that such a mixture contains at least 5% by weight of the    aminocyclohexanealkylamine-initiated polyol of the first aspect;-   2) at least one hydrocarbon, hydrofluorocarbon,    hydrochlorofluorocarbon, fluorocarbon, dialkyl ether or    fluorine-substituted dialkyl ether physical blowing agent; and-   3) at least one polyisocyanate; and-   b) subjecting the reactive mixture to conditions such that the    reactive mixture expands and cures to form a rigid polyurethane    foam.

In another aspect, the invention is a rigid foam made in accordance withthe foregoing process.

It has been found that rigid foam formulations that include the polyolof the invention often exhibit desirable curing characteristics (asindicated by flow index of below 1.8) and short demold times, and cureto form a foam having excellent thermal insulation properties (i.e., lowk-factor). These advantages are seen particularly when theamine-initiated polyol of the invention is used in an admixture thatcontains one or more other polyols that have a hydroxyl functionality offrom 4 to 8 and a hydroxyl equivalent weight from 75 to 200.

The amine-initiated polyol is a polyether that is prepared from at leastone aminocyclohexanealkylamine initiator compound. For purposes of thisinvention, an “aminocyclohexanealkylamine” initiator compound is onehaving a cyclohexane group that is substituted on the cyclohexane ringwith a primary amino (—NH₂) group, and which is also substituted on thecyclohexane group with at least one, and preferably only one, aminoalkylgroup. The aminoalkyl group can be represented as —(CR₂)_(m)—NH₂,wherein each R is independently hydrogen or C₁-C₄ alkyl and m is anumber from 1 to 8. Each R is preferably independently hydrogen ormethyl. The primary amino group and the aminoalkyl group(s) can be inthe ortho, meta or para positions with respect to each other, and may bein the cis- (both on the same side of the ring) or trans- (located onopposite sides of the ring) positions with respect to each other. Thecyclohexane ring may also contain inert substitution. “Inert”substitution is substitution that (1) is not reactive with an alkyleneoxide under the conditions of alkoxylation (as described more below),(2) is not reactive with isocyanate groups and (3) does notsignificantly affect the ability of the aminocyclohexanealkylaminecompound to become alkoxylated and of the resulting polyol to react witha polyisocyanate to form urethane linkages. Inert substitution includeshydrocarbyl substitution such as alkyl, alkenyl, alkynylaryl,aryl-substituted alkyl, cycloalkyl and the like, ether groups, tertiaryamino groups, and the like. It is preferred that any substituent groupsthat may be present are C₁-C₄ alkyl, especially methyl. It is especiallypreferred that the cyclohexane ring is methyl-substituted at the carbonatom to which the amino group is bonded.

Mixtures of two or initiator compounds as just described can be used.Initiators of the foregoing structure may exist in two or morediastereoisomeric forms. In such cases, any of the diastereoisomericforms, or mixtures of any two or more of the diastereoisomeric forms,can be used.

One class of aminocyclohexanealkylamine compounds includes thoserepresented by structure I:

wherein R¹ is C₁-C₄ alkyl, and R and m are as defined before. Each Rgroup in structure I is preferably independently hydrogen or methyl, andR¹ is preferably methyl. In structure I, the —(CR₂)_(m)—NH₂ group may beortho, meta or para to the amino group bonded directly to thecyclohexane ring. The —NH₂ and —(CR₂)_(m)—NH₂ groups in structure I maybe in the cis- or trans-positions with respect to each other. Instructure I, the cyclohexane carbon atoms may contain inert substituentgroups in addition to the —NH₂, —R¹ and —(CR₂)_(m)—NH₂ groups shown. Apreferred initiator compound corresponding to structure I iscyclohexanemethanamine, 4-amino-α,α,4-trimethyl-(9Cl), which is alsoknown as p-menthane-1,8-diamine or 1,8-diamino-p-menthane. This compoundexists in two diastereoisomeric forms, as follows:

Either of the diastereoisomeric forms, or a mixture of both, can beused.

A second type of aminocyclhexanealkylamine initiator corresponds tostructure II:

in which R, R₁ and m are as defined before. As in structure I, each Rgroup in structure II is preferably independently hydrogen or methyl andR¹ is preferably methyl. In structure II, the —(CR₂)_(m)—NH₂ group maybe ortho, meta or para to the amino group bonded directly to thecyclohexane ring. The —NH₂ and —(CR₂)_(m)—NH₂ groups in structure II maybe in the cis- or trans-positions with respect to each other. Instructure II, the cyclohexane carbon atoms may contain inert substituentgroups in addition to the —NH₂, —R¹ and —(CR₂)_(m)—NH₂ groups shown. Anespecially preferred initiator compound that corresponds to structure IIis 5-amino-1,3,3-trimethylcyclohexanemethylamine, which is commonlyknown as isophoronediamine. Isophoronediamine also exists in twodiastereoisomeric forms, as follows:

Again, either of these forms or a mixture thereof can be used.

Commercially available aminocyclohexanealkylamine compounds tend tocontain small amounts (typically less than 3% by weight) of impurities,which tend to be mainly other amine or diamine compounds. Thesecommercially materials are suitable as initiators in the presentinvention.

The initiator compound is caused to react with at least one C₂-C₄alkylene oxide to produce the amine-initiated polyol of the invention.The alkylene oxide may be ethylene oxide, propylene oxide, 1,2- or2,3-butylene oxide, tetramethylene oxide or a combination of two or morethereof. If two or more alkylene-oxides are used, they may be added tothe initiator compound simultaneously (to form a random copolymer) orsequentially (to form a block copolymer). Butylene oxide andtetramethylene oxide are generally less preferred. Ethylene oxide,propylene oxide and mixtures thereof are more preferred. Mixtures ofethylene oxide and propylene oxide may contain the oxides in anyproportion. For example, a mixture of ethylene oxide and propylene oxidemay contain from 10 to 90 weight percent of ethylene oxide, preferablyfrom 30 to 70 weight percent ethylene oxide or from 40 to 60 weightpercent ethylene oxide.

Enough of the alkylene oxide(s) are added to the initiator to produce apolyol having an average hydroxyl functionality of greater than 3.0, upto as many as 4.0 hydroxyl groups/molecule. A preferred average hydroxylfunctionality for the polyol is from 3.3 to 4.0, and a more preferredaverage hydroxyl functionality is from 3.7 to 4.0. A polyol of theinvention that is useful for preparing rigid polyurethane foam suitablyhas a hydroxyl equivalent weight of from 75 to 560. A preferred hydroxylequivalent weight for rigid foam production is from 90 to 175 and a morepreferred hydroxyl equivalent weight for rigid foam production is from100 to 130.

The alkoxylation reaction is conveniently performed by forming a mixtureof the alkylene oxide(s) and the initiator compound, and subjecting themixture to conditions of elevated temperature and superatmosphericpressure. Polymerization temperatures may be, for example, from 110 to170° C., and pressures may be, for example, from 2 to 10 bar (200 to1000 kPa). A catalyst may be used, particularly if more than one mole ofalkylene oxide(s) is to be added per equivalent of amine hydrogen on theinitiator compound. Suitable alkoxylation catalysts include strong basessuch as alkali metal hydroxides (sodium hydroxide, potassium hydroxide,cesium hydroxide, for example), as well as the so-called double metalcyanide catalysts (of which zinc hexacyanocobaltate complexes are mostnotable). The reaction can be performed in two or more stages, in whichno catalyst is used in the first stage, and from 0.5 to 1.0 mole ofalkylene oxide is added to the initiator per equivalent of aminehydrogens, followed by one or more subsequent stages in which additionalalkylene oxide is added in the presence of a catalyst as described.After the reaction is completed, the catalyst may be deactivated and/orremoved. Alkali metal hydroxide catalysts may be removed, left in theproduct, or neutralized with an acid and the residues left in theproduct. Residues of double metal cyanide catalysts may be left in theproduct, but can be removed instead if desired.

Preferred amine-initiated polyols are (a) the reaction product ofisophorone diamine or 1,8-diamino-p-menthane with ethylene oxide, (b)the reaction product of isophorone diamine or 1,8-diamino-p-menthanewith propylene oxide and (c) the reaction product of isophorone diamineor 1,8-diamino-p-menthane with a mixture of from 30 to 70 mole percentethylene oxide and 70 to 30 mole percent propylene oxide, in each casehaving a hydroxyl functionality of from 3.3 to 4.0, especially 3.7 to4.0 and a hydroxyl equivalent weight of from 90 to 175, especially from100 to 130.

The amine-initiated polyol of the invention is useful in preparing rigidpolyurethane foam, particularly when its hydroxyl equivalent weight isfrom 75 to 560. The rigid polyurethane foam is prepared from apolyurethane-forming composition that contains at least (1) theamine-initiated polyol, optionally in combination with one or more otherpolyols, (2) at least one organic polyisocyanate, and (3) at least onephysical blowing agent as described more fully below.

The amine-initiated polyol of the invention suitably constitutes atleast 5 weight percent of all polyols present in thepolyurethane-forming composition. Below this level, the benefits ofusing the polyol are slight. The amine-initiated polyol of the inventionmay be the sole polyol in the polyurethane-forming composition. However,it is anticipated that in most cases, it will be used in a mixturecontaining at least one other polyol, and that the amine-initiatedpolyol of the invention will constitute from about 5 to about 75% byweight of the polyol mixture. For example, the amine-initiated polyol ofthe invention may constitute from 10 to about 60% by weight of thepolyol mixture, or from about 10 to about 50% by weight of the polyolmixture.

When a mixture of polyols is used, the polyol mixture preferably has anaverage of 3.5 to about 7 hydroxyl groups/molecule and an averagehydroxyl equivalent weight of about 90 to about 175. Any individualpolyol within the mixture may have a functionality and/or equivalentweight outside of those ranges, if the mixture meets these parameters.Water is not considered in determining the functionality or equivalentweight of a polyol mixture.

A more preferred average hydroxyl functionality for a polyol mixture isfrom about 3.8 to about 6 hydroxyl groups/molecule. An even morepreferred average hydroxyl functionality for a polyol mixture is fromabout 3.8 to about 5 hydroxyl groups/molecule. A more preferred averagehydroxyl equivalent weight for a polyol mixture is from about 110 toabout 130.

Suitable polyols that can be used in conjunction with theamine-initiated polyol of the invention include polyether polyols, whichare conveniently made by polymerizing an alkylene oxide onto aninitiator compound (or mixture of initiator compounds) that has multipleactive hydrogen atoms. The initiator compound(s) may include alkyleneglycols (e.g., ethylene glycol, propylene glycol, 1,4-butane diol,1,6-hexanediol and the like), glycol ethers (such as diethylene glycol,triethylene glycol, dipropylene glycol, tripropylene glycol and thelike), glycerine, trimethylolpropane, pentaerythritol, sorbitol,sucrose, glucose, fructose or other sugars, and the like. A portion ofthe initiator compound may be one containing primary and/or secondaryamino groups, such as ethylene diamine, hexamethylene diamine,diethanolamine, monoethanolamine, N-methyldiethanolamine, piperazine,aminoethylpiperazine, diisopropanolamine, monoisopropanolamine,methanolamine, dimethanolamine, toluene diamine (all isomers) and thelike. Amine-initiated polyols of these types tend to be somewhatautocatalytic. The alkylene oxides used to make the additional polyol(s)are as described before with respect to the amine-initiated polyol ofthe invention. The alkylene oxide of choice is propylene oxide, or amixture of propylene oxide and ethylene oxide.

Polyester polyols may also be used as an additional polyol, but aregenerally less preferred as they tend to have lower functionalities. Thepolyester polyols include reaction products of polyols, preferablydiols, with polycarboxylic acids or their anhydrides, preferablydicarboxylic acids or dicarboxylic acid anhydrides. The polycarboxylicacids or anhydrides may be aliphatic, cycloaliphatic, aromatic and/orheterocyclic and may be substituted, such as with halogen atoms. Thepolycarboxylic acids may be unsaturated. Examples of thesepolycarboxylic acids include succinic acid, adipic acid, terephthalicacid, isophthalic acid, trimellitic anhydride, phthalic anhydride,maleic acid, maleic acid anhydride and fumaric acid. The polyols used inmaking the polyester polyols include ethylene glycol, 1,2- and1,3-propylene glycol, 1,4- and 2,3-butane diol, 1,6-hexane diol,1,8-octane diol, neopentyl glycol, cyclohexane dimethanol,2-methyl-1,3-propane diol, glycerine, trimethylol propane, 1,2,6-hexanetriol, 1,2,4-butane triol, trimethylol ethane, pentaerythritol,quinitol, mannitol, sorbitol, methyl glycoside, diethylene glycol,triethylene glycol, tetraethylene glycol, dipropylene glycol, dibutyleneglycol and the like.

In a preferred embodiment, the amine-initiated polyol of the inventionis used as a mixture with at least one other polyether polyol that hasan average functionality of from 4.5 to 7 hydroxyl groups per moleculeand a hydroxyl equivalent weight of 100 to 175. The other polyetherpolyol may be, for example, a sorbitol- or sucrose/glycerine-initiatedpolyether. The amine-initiated polyol of the invention may constitutefrom 10 to 70% of the weight of the mixture in this case. Examples ofsuitable sorbitol- or sucrose/glycerine-initiated polyethers that can beused include Voranol® 360, Voranol® RN411, Voranol® RN490, Voranol® 370,Voranol® 446, Voranol® 520, Voranol® 550 and Voranol® 482 polyols, allavailable from Dow Chemical.

In another preferred embodiment, the amine-initiated polyol of theinvention is used in a polyol mixture that also contains at least oneother polyether polyol that has an average functionality of from 4.5 to7 hydroxyl groups per molecule and a hydroxyl equivalent weight of 100to 175, and which is not amine-initiated, and at least one otheramine-initiated polyol having an average functionality of from 2.0 to4.0 (preferably 3.0 to 4.0) and a hydroxyl equivalent weight of from 100to 225. The other amine-initiated polyol may be initiated with, forexample, ammonia, ethylene diamine, hexamethylenediamiane,diethanolamine, monoethanolamine, N-methyldiethanolamine, piperazine,aminoethylpiperazine, diisopropanolamine, monoisopropanolamine,methanolamine, dimethanolamine, toluene diamine (all isomers) and thelike. Ethylene diamine- and toluene diamine-initiated polyols arepreferred in this case. The polyol mixture may contain from 5 to 50% byweight of the amine-initiated polyol of the invention; from 20 to 70% byweight of the non-amine-initiated polyol and from 2 to 20% by weight ofthe other amine-initiated polyol. The polyol mixture may contain up to15% by weight of still another polyol, which is not amine-initiated andwhich has a hydroxyl functionality of 2.0 to 3.0 and a hydroxylequivalent weight of from 90 to 500, preferably from 200 to 500.Specific examples of polyol mixtures as just described include a mixtureof from 5 to 50% by weight of the amine-initiated polyol of theinvention, from 20 to 70% of a sorbitol or sucrose/glycerine initiatedpolyether polyol having an average functionality of from 4.5 to 7hydroxyl groups per molecule and a hydroxyl equivalent weight of 100 to175, from 2 to 20% by weight of an ethylenediamine-initiated polyolhaving an equivalent weight of from 100 to 225, and from 0 to 15% byweight of a non-amine-initiated polyol having a functionality of from2.0 to 3.0 and hydroxyl equivalent weight of from 200 to 500.

Polyol mixtures as described can be prepared by making the constituentpolyols individually, and then blending them together. Alternatively,polyol mixtures can be prepared by forming a mixture of the respectiveinitiator compounds, and then alkoxylating the initiator mixture to formthe polyol mixture directly. Such “co-initiated” polyols may be preparedusing the aminocyclohexanealkylamine and another amine as theinitiators, to form a blend of amine-initiated polyols. Combinations ofthese approaches can also be used.

The polyurethane-forming composition contains at least one organicpolyisocyanate. The organic polyisocyanate or mixture thereofadvantageously contains an average of at least 2.5 isocyanate groups permolecule. A preferred isocyanate functionality is from about 2.5 toabout 3.6 or from about 2.6 to about 3.3 isocyanate groups/molecule. Thepolyisocyanate or mixture thereof advantageously has an isocyanateequivalent weight of from about 130 to 200. This is preferably from 130to 185 and more preferably from 130 to 170. These functionality andequivalent weight values need not apply with respect to any singlepolyisocyanate in a mixture, provided that the mixture as a whole meetsthese values.

Suitable polyisocyanates include aromatic, aliphatic and cycloaliphaticpolyisocyanates. Aromatic polyisocyanates are generally preferred.Exemplary polyisocyanates include, for example, m-phenylenediisocyanate, 2,4- and/or 2,6-toluene diisocyanate (TDI), the variousisomers of diphenylmethanediisocyanate (MDI),hexamethylene-1,6-diisocyanate, tetramethylene-1,4-diisocyanate,cyclohexane-1,4-diisocyanate, hexahydrotoluene diisocyanate,hydrogenated MDI (H₁₂ MDI), naphthylene-1,5-diisocyanate,methoxyphenyl-2,4-diisocyanate, 4,4′-biphenylene diisocyanate,3,3′-dimethyoxy-4,4′-biphenyl diisocyanate,3,3′-dimethyldiphenylmethane-4,4′-diisocyanate, 4,4′,4″-triphenylmethanediisocyanate, polymethylene polyphenylisocyanates, hydrogenatedpolymethylene polyphenyl polyisocyanates, toluene-2,4,6-triisocyanateand 4,4′-dimethyldiphenylmethane-2,2′,5,5′-tetraisocyanate. Preferredpolyisocyanates are the so-called polymeric MDI products, which are amixture of polymethylene polyphenylene polyisocyanates in monomeric MDI.Especially suitable polymeric MDI products have a free MDI content offrom 5 to 50% by weight, more preferably 10 to 40% by weight. Suchpolymeric MDI products are available from The Dow Chemical Company underthe trade names PAPI® and Voranate®.

An especially preferred polisocyanate is a polymeric MDI product havingan average isocyanate functionality of from 2.6 to 3.3 isocyanategroups/molecule and an isocyanate equivalent weight of from 130 to 170.Suitable commercially available products of that type include PAPI™ 27,Voranate™ M229, Voranate™ 220, Voranate™ 290, Voranate™ M595 andVoranate™ M600, all from Dow Chemical.

Isocyanate-terminated prepolymers and quasi-prepolymers (mixtures ofprepolymers with unreacted polyisocyanate compounds) can also be used.These are prepared by reacting a stoichiometric excess of an organicpolyisocyanate with a polyol, such as the polyols described above.Suitable methods for preparing these prepolymers are well known. Such aprepolymer or quasi-prepolymer preferably has an isocyanatefunctionality of from 2.5 to 3.6 and an isocyanate equivalent weight offrom 130 to 200.

The polyisocyanate is used in an amount sufficient to provide anisocyanate index of from 80 to 600. Isocyanate index is calculated asthe number of reactive isocyanate groups provided by the polyisocyanatecomponent divided by the number of isocyanate-reactive groups in thepolyurethane-forming composition (including those contained byisocyanate-reactive blowing agents such as water) and multiplying by100. Water is considered to have two isocyanate-reactive groups permolecule for purposes of calculating isocyanate index. A preferredisocyanate index is from 90 to 400 and a more preferred isocyanate indexis from 100 to 150.

The blowing agent used in the polyurethane-forming composition includesat least one physical blowing agent which is a hydrocarbon,hydrofluorocarbon, hydrochlorofluorocarbon, fluorocarbon, dialkyl etheror fluorine-substituted dialkyl ethers, or a mixture of two or morethereof. Blowing agents of these types include propane, isopentane,n-pentane, n-butane, isobutene, isobutene, cyclopentane, dimethyl ether,1,1-dichloro-1-fluoroethane (HCFC-141b), chlorodifluoromethane(HCFC-22), 1-chloro-1,1-difluoroethane (HCFC-142b),1,1,1,2-tetrafluoroethane (HFC-134a), 1,1,1,3,3-pentafluorobutane(HFC-365mfc), 1,1-difluoroethane (HFC-152a),1,1,1,2,3,3,3-heptafluoropropane (HFC-227ea) and1,1,1,3,3-pentafluoropropane (HFC-245fa). The hydrocarbon andhydrofluorocarbon blowing agents are preferred. It is generallypreferred to further include water in the formulation, in addition tothe physical blowing agent.

Blowing agent(s) are preferably used in an amount sufficient such thatthe formulation cures to form a foam having a molded density of from 16to 160 kg/m³, preferably from 16 to 64 kg/m³ and especially from 20 to48 kg/m³. To achieve these densities, the hydrocarbon orhydrofluorocarbon blowing agent conveniently is used in an amountranging from about 10 to about 40, preferably from about 12 to about 35,parts by weight per 100 parts by weight polyol(s). Water reacts withisocyanate groups to produce carbon dioxide, which acts as an expandinggas. Water is suitably used in an amount within the range of 0.5 to 3.5,preferably from 1.5 to 3.0 parts by weight per 100 parts by weight ofpolyol(s).

The polyurethane-forming composition typically will include at least onecatalyst for the reaction of the polyol(s) and/or water with thepolyisocyanate. Suitable urethane-forming catalysts include thosedescribed by U.S. Pat. No. 4,390,645 and in WO 02/079340, bothincorporated herein by reference. Representative catalysts includetertiary amine and phosphine compounds, chelates of various metals,acidic metal salts of strong acids; strong bases, alcoholates andphenolates of various metals, salts of organic acids with a variety ofmetals, organometallic derivatives of tetravalent tin, trivalent andpentavalent As, Sb and Bi and metal carbonyls of iron and cobalt.

Tertiary amine catalysts are generally preferred. Among the tertiaryamine catalysts are dimethylbenzylamine (such as Desmorapid® DB fromRhine Chemie), 1,8-diaza (5,4,0)undecane-7 (such as Polycat® SA-1 fromAir Products), pentamethyldiethylenetriamine (such as Polycat® 5 fromAir Products), dimethylcyclohexylamine (such as Polycat® 8 from AirProducts), triethylene diamine (such as Dabco® 33LV from Air Products),dimethyl ethyl amine, n-ethyl morpholine, N-alkyl dimethylaminecompounds such as N-ethyl N,N-dimethyl amine and N-cetylN,N-dimethylamine, N-alkyl morpholine compounds such as N-ethylmorpholine and N-coco morpholine, and the like. Other tertiary aminecatalysts that are useful include those sold by Air Products under thetrade names Dabco® NE1060, Dabco® NE1070, Dabco® NE500, Dabco® TMR-2,Dabco® TMR 30, Polycat® 1058, Polycat® 11, Polycat 15, Polycat® 33Polycat® 41 and Dabco® MD45, and those sold by Huntsman under the tradenames ZR 50 and ZR 70. In addition, certain amine-initiated polyols canbe used herein as catalyst materials, including those described in WO01/58976 A. Mixtures of two or more of the foregoing can be used.

The catalyst is used in catalytically sufficient amounts. For thepreferred tertiary amine catalysts, a suitable amount of the catalystsis from about 1 to about 4 parts, especially from about 1.5 to about 3parts, of tertiary amine catalyst(s) per 100 parts by weight of thepolyol(s).

The polyurethane-forming composition also preferably contains at leastone surfactant, which helps to stabilize the cells of the composition asgas evolves to form bubbles and expand the foam. Examples of suitablesurfactants include alkali metal and amine salts of fatty acids, such assodium oleate, sodium stearate sodium ricinolates, diethanolamineoleate, diethanolamine stearate, diethanolamine ricinoleate, and thelike: alkali metal and amine salts of sulfonic acids such asdodecylbenzenesulfonic acid and dinaphthylmethanedisulfonic acid;ricinoleic acid; siloxane-oxalkylene polymers or copolymers and otherorganopolysiloxanes; oxethylated alkylphenols (such as Tergitol NP9 andTriton X100, from The Dow Chemical Company); oxyethylated fatty alcoholssuch as Tergitol 15-S-9, from The Dow Chemical Company; paraffin oils;castor oil; ricinoleic acid esters; turkey red oil; peanut oil;paraffins; fatty alcohols; dimethyl polysiloxanes and oligomericacrylates with polyoxyalkylene and fluoroalkane side groups. Thesesurfactants are generally used in amount of 0.01 to 6 parts by weightbased on 100 parts by weight of the polyol.

Organosilicone surfactants are generally preferred types. A wide varietyof these organosilicone surfactants are commercially available,including those sold by Goldschmidt under the Tegostab® name (such asTegostab B-8462, B8427, B8433 and B-8404 surfactants), those sold by OSiSpecialties under the Niax® name (such as Niax® L6900 and L6988surfactants) as well as various surfactant products commerciallyavailable from Air Products and Chemicals, such as DC-193, DC-198,DC-5000, DC-5043 and DC-5098 surfactants.

In addition to the foregoing ingredients, the polyurethane-formingcomposition may include various auxiliary components, such as fillers,colorants, odor masks, flame retardants, biocides, antioxidants, UVstabilizers, antistatic agents, viscosity modifiers, and the like.

Examples of suitable flame retardants include phosphorus compounds,halogen-containing compounds and melamine.

Examples of fillers and pigments include calcium carbonate, titaniumdioxide, iron oxide, chromium oxide, azo/diazo dyes, phthalocyanines,dioxazines, recycled rigid polyurethane foam and carbon black.

Examples of UV stabilizers include hydroxybenzotriazoles, zinc dibutylthiocarbamate, 2,6-ditertiarybutyl catechol, hydroxybenzophenones,hindered amines and phosphites.

Except for fillers, the foregoing additives are generally used in smallamounts, such as from 0.01 percent to 3 percent each by weight of thepolyurethane formulation. Fillers may be used in quantities as high as50% by weight of the polyurethane formulation.

The polyurethane-forming composition is prepared by bringing the variouscomponents together under conditions such that the polyol(s) andisocyanate(s) react, the blowing agent generates a gas, and thecomposition expands and cures. All components (or any sub-combinationthereof) except the polyisocyanate can be pre-blended into a formulatedpolyol composition, if desired, which is then mixed with thepolyisocyanate when the foam is to be prepared. The components may bepreheated if desired, but this is usually not necessary, and thecomponents can be brought together at about room temperature (˜22° C.)to conduct the reaction. It is usually not necessary to apply heat tothe composition to drive the cure, but this may be done if desired, too.

The invention is particularly useful in so-called “pour-in-place”applications, in which the polyurethane-forming composition is dispensedinto a cavity and foams within the cavity to fill it and providestructural and/or thermal insulative attributes to an assembly. Thenomenclature “pour-in-place” refers to the fact that the foam is createdat the location where it is needed, rather than being created in onestep and later assembled into place in a separate manufacturing step.Pour-in-place processes are commonly used to make appliance productssuch as refrigerators, freezers, and coolers and similar products whichhave walls that contain thermal insulation foam. The presence of theamine-initiated polyol in the polyurethane-forming composition tends toprovide the formulation with good flow and short demold times, while atthe same time producing a low k-factor foam.

The walls of appliances such as refrigerators, freezers and coolers aremost conveniently insulated in accordance with the invention by firstassembling an outer shell and in interior liner together, such that acavity is formed between the shell and liner. The cavity defines thespace to be insulated as well as the dimensions and shape of the foamthat is produced. Typically, the shell and liner are bonded together insome way, such as by welding, melt-bonding or through use of someadhesive (or some combination of these) prior to introduction of thefoam formulation. The shell and liner may be supported or held in thecorrect relative positions using a jig or other apparatus. One or moreinlets to the cavity are provided, through which the foam formulationcan be introduced. Usually, one or more outlets are provided to allowair in the cavity to escape as the cavity is filled with the foamformulation and the foam formulation expands.

The materials of construction of the shell and liner are notparticularly critical, provided that they can withstand the conditionsof the curing and expansion reactions of the foam formulation. In mostcases, the materials of construction will be selected with regard tospecific performance attributes that are desired in the final product.Metals such as steel are commonly used as the shell, particularly inlarger appliances such as freezers or refrigerators. Plastics such aspolycarbonates, polypropylene, polyethylene styrene-acrylonitrileresins, acrylonitrile-butadiene-styrene resins or high-impactpolystyrene are used more often to make the shells for smallerappliances (such as coolers) or those in which low weight is important.The liner may be a metal, but is more typically a plastic as justdescribed.

The foam formulation is then introduced into the cavity. The variouscomponents of the foam formulation are mixed together and the mixtureintroduced quickly into the cavity, where the components react andexpand. It is common to pre-mix the polyol(s) together with the waterand blowing agent (and often catalyst and/or surfactant as well) toproduce a formulated polyol. The formulated polyol can be stored untilit is time to prepare the foam, at which time it is mixed with thepolyisocyanate and introduced into the cavity. It is usually notrequired to heat the components prior to introducing them into thecavity, nor it is usually required to heat the formulation within thecavity to drive the cure, although either or both of these steps may betaken if desired. The shell and liner may act as a heat sink in somecases, and remove heat from the reacting foam formulation. If necessary,the shell and/or liner can be heated somewhat (such as up to 50° C. andmore typically 35-40° C.) to reduce this heat sink effect, or to drivethe cure.

Enough of the foam formulation is introduced such that, after it hasexpanded, the resulting foam fills those portions of the cavity wherefoam is desired. Most typically, essentially the entire cavity is filledwith foam. It is generally preferred to “overpack” the cavity slightly,by introducing more of the foam formulation than is minimally needed tofill the cavity, thereby increasing the foam density slightly. Theoverpacking provides benefits such as better dimensional stability ofthe foam, especially in the period following demold. Generally, thecavity is overpacked by from 4 to 20% by weight. The final foam densityfor most appliance applications is preferably in the range of from 28 to40 kg/m³.

After the foam formulation has expanded and cured enough to bedimensionally stable, the resulting assembly can be “demolded” byremoving it from the jig or other support that is used to maintain theshell and liner in their correct relative positions. Short demold timesare important to the appliance industry, as shorter demold times allowmore parts to be made per unit time on a given piece of manufacturingequipment.

Demold times can be evaluated as follows: A 28-liter “jumbo” Brett moldcoated with release agent is conditioned to a temperature of 45° C. 896g±4 g of a foam formulation is injected into the mold in order to obtaina 32 kg/m³ density foam. After a period of 6 minutes, the foam isremoved from the mold and the thickness of the foam is measured. After afurther 24 hours, the foam thickness is re-measured. The differencebetween the thickness after 24 hours and the initial thickness is anindication of the post-demold expansion of the foam. The demold time isconsidered to be sufficiently long if the post-demold expansion is nomore than 4 mm on this test.

As mentioned, flow is another important attribute of the foamformulation. For purposes of this invention, flow is evaluated using arectangular “Brett” mold, having dimensions of 200 cm×20 cm×5 cm(˜6′6″×8″×2″). The polyurethane-forming composition is formed, andimmediately injected into the Brett mold, which is oriented vertically(i.e., 200 cm direction oriented vertically) and preheated to 45±5° C.The composition is permitted to expand against its own weight and cureinside the mold. The amount of polyurethane-forming composition isselected such that the resulting foam just fills the mold. The densityof the resulting foam is then measured and compared with the density ofa free-rise foam made from the same formulation (by injecting theformulation into a plastic bag or open cardboard box where it can expandfreely vertically and horizontally against atmospheric pressure). Theratio of the Brett mold foam density to the free rise density isconsidered to represent the “flow index” of the formulation. With thisinvention, flow index values are typically below 1.8, and are preferablyfrom 1.2 to 1.5.

The polyurethane foam advantageously exhibits a low k-factor. Thek-factor of a foam may depend on several variables, of which density isan important one. For many applications, a rigid polyurethane foamhaving a density of from 28.8 to 40 kg/m³ (1.8 to 2.5 pounds/cubic foot)exhibits a good combination of physical properties, dimensionalstability, and cost. Foam in accordance with the invention, having adensity within that range, preferably exhibits a 10° C. k-factor of nogreater than 22, preferably no greater than 20, and more preferably nogreater than 19.5 mW/m-° K. Higher density foam may exhibit a somewhathigher k-factor.

In addition to the appliance and thermal insulation foams describedabove, the invention is also useful to produce vehicle noise dampeningfoams, one or more layers of a laminated board, pipe insulation andother foam products. The invention is of special interest when a rapidcure is wanted, and or good thermal insulating properties are wanted inthe foam.

If desired, the process of the invention can be practiced in conjunctionwith the methods described, for example, in WO 07/058793, in which thereaction mixture is injected into a closed mold cavity which is at areduced pressure.

The following examples are provided to illustrate the invention, but arenot intended to limit the scope thereof. All parts and percentages areby weight unless otherwise indicated.

EXAMPLE 1

A mixture of the cis- and trans-isomers of isophorone diamine (fromSigma-Aldrich, Gillingham, UK) (5015 g, 29.5 moles) is added to a glassreactor purged with nitrogen, and heated to 125° C. The flask ispressurized to ˜4500 kPa with propylene oxide, and the pressuremaintained until a total of 5133 g (88.4 mole) of propylene oxide is fedto the flask. The reaction is then allowed to digest for two hours at125° C., after which 79.4 g of a 45% potassium hydroxide solution inwater is added. The water is removed under vacuum at 115° C., and thereactor is again heated to 125° C. More propylene oxide is fed into thereactor at a rate of 30 g/minute until an additional 4356 g (75 mol) ofpropylene oxide is added. The reaction is then allowed to digest againfor 2 hours, at which time 56.7 g of an 70% solution of acetic acid inwater is added. The resulting polyol has a hydroxyl number of 440 mgKOH/g (corresponding to a hydroxyl equivalent weight of 127.5) and ahydroxyl functionality of close to 4.0. The polyol has a viscosity of23,800 centipoises at 50° C.

EXAMPLE 2

Rigid polyurethane foam is produced from the components described inTable 1. Foam processing is performed using a Hi Tech CS-50 highpressure machine operated at a throughput of 175-225 g/s. The foamformulation is injected into a bag (to measure free rise density) andinto a vertical Brett mold which is preheated to 45° C. Componenttemperatures prior to mixing are ˜21° C.

TABLE 1 Component Parts By Weight Sorbitol-initiated polyol¹ 57.0 Polyolof Example 1 15.6 Ethylene diamine-initiated polyol² 11.0 Poly(propyleneoxide) diol³ 10.0 Water 2.4 Silicone surfactant 2.0 Amine Catalysts 2.0Cyclopentane 14.0 Polymeric MDI⁴ (index) 144 (115 index) ¹A 6.0functional poly(propylene oxide) having a hydroxyl number of 482,commercially available as Voranol ® RN 482 polyol from Dow Chemical. ²Apoly(propylene oxide) having a hydroxyl number of 500, commerciallyavailable as Voranol ® RA 500 polyol from Dow Chemical. ³A diol having amolecular weight of about 400, commercially available as Voranol ® P400polyol from Dow Chemical. ⁴Voranate ™ M229 polymeric MDI, available fromDow Chemical.

The composition has a cream time of 3.5 seconds, a gel time of 33seconds and a tack-free time of 41 seconds. The free rise density is22.28 kg/m³, and the minimum fill density is 32.1 kg/m³. The flow indexis therefore 1.441. The foam has an average compressive strength of145.62 kPa.

K-factor is measured on 8″×1″×1″ (20×2.5×2.5 cm) samples using a LaserComp Fox 200 device, with an upper cold plate temperature of 10° C. anda lower warm plate temperature of 38° C., and found to be 19.15 mW/m-°K.

1. An amine-initiated polyol having an average functionality of greaterthan 3.0 up to 4.0, the polyol being a reaction product of at least oneC₂-C₄ alkylene oxide with an aminocylohexanealkylamine initiatorcompound.
 2. The amine-initiated polyol of claim 1 having afunctionality of from 3.3 to 4.0 and a hydroxyl equivalent weight offrom 75 to
 560. 3-4. (canceled)
 5. The amine-initiated polyol of claim 2wherein the initiator compound is represented by either of thestructures:

wherein each R is independently hydrogen or C₁-C₄ alkyl, R¹ is C₁-C₄alkyl, and m is a number from 1 to
 8. 6. The amine-initiated polyol ofclaim 5 having a functionality of 3.7 to 4.0 and a hydroxyl equivalentweight of from 100 to
 130. 7. The amine-initiated polyol of claim 6,wherein the alkylene oxide is ethylene oxide, propylene oxide or amixture of ethylene oxide and propylene oxide.
 8. The amine-initiatedpolyol of claim 7 wherein the initiator compound is isophorone diamine.9. The amine-initiated polyol of claim 7 wherein the initiator compoundis 1,8-diamino-p-menthane.
 10. A process for preparing a rigidpolyurethane foam, comprising a) forming a reactive mixture containingat least 1) an amine-initiated polyol of claim 2, or mixture thereofwith at least one other polyol, provided that such a mixture contains atleast 5% by weight of the amine-initiated polyol of claim 2; 2) at leastone hydrocarbon, hydrofluorocarbon, hydrochlorofluorocarbon,fluorocarbon, dialkyl ether or fluorine-substituted dialkyl etherphysical blowing agent; and 3) at least one polyisocyanate; and b)subjecting the reactive mixture to conditions such that the reactivemixture expands and cures to form a rigid polyurethane foam.
 11. Theprocess of claim 10, wherein the initiator compound is represented byeither of the structures:

wherein each R is independently hydrogen or C₁-C₄ alkyl, R¹ is C₁-C₄alkyl, and m is a number from 1 to
 8. 12. The process of claim 11,wherein the reactive mixture further contains water.
 13. The process ofclaim 12 wherein the amine-initiated polyol has a functionality of 3.7to 4.0 and a hydroxyl equivalent weight of from 100 to
 130. 14. Theprocess of claim 13, wherein the amine-initiated polyol is a reactionproduct of isophorone diamine and a C₂-C₄ alkylene oxide.
 15. Theprocess of claim 14, wherein the alkylene oxide is ethylene oxide,propylene oxide or a mixture of ethylene oxide and propylene oxide. 16.The process of claim 13, wherein the amine-initiated polyol is areaction product of 1,8-diamino-p-menthane and a C₂-C₄ alkylene oxide.17-18. (canceled)
 19. The process of claim 16, wherein the reactionmixture contains a mixture of the amine-initiated polyol and at leastone at least one polyether polyol having a functionality of from 4.5 to7 and a hydroxyl equivalent weight of 100 to
 175. 20. The process ofclaim 19, wherein the reaction mixture further contains at least onedifferent amine-initiated polyol having an average functionality of from2.0 to 4.0 and a hydroxyl equivalent weight of from 100 to
 225. 21. Theprocess of claim 20, wherein the reaction mixture further contains anon-amine-initiated polyol having a functionality of from 2.0 to 3.0 anda hydroxyl equivalent weight of from 90 to
 500. 22. A rigid polyurethanefoam made in accordance with claim
 10. 23. The foam of claim 22, whichis an appliance insulation foam, a layer of a laminated board, pipeinsulation or a vehicle dampening member.
 24. (canceled)
 25. A polyolmixture comprising: a) from 10 to 50%, based on the combined weights ofcomponents a), b), c) and d), of an amine-initiated polyol of claim 2;b) from 20 to 70%, based on the combined weights of components a), b),c) and d), of a non-amine-initiated polyether polyol having an averagefunctionality of from 4.5 to 7 and a hydroxyl equivalent weight of from100 to 175; c) from 2 to 20%, based on the combined weights ofcomponents a), b), c) and d), of another amine-initiated polyol,different from component a), which has an average functionality of from2.0 to 4.0 and a hydroxyl equivalent weight of from 100 to 225 and d)from 0 to 15%, based on the combined weights of components a), b), c)and d), of a non-amine-initiated polyol having a functionality of from2.0 to 30 and a hydroxyl equivalent weight of from 200 to 500.